A biomass boiler is a boiler that burns thing like, logs and anything made of plant or tree material.With modern biomass burners there is very little ash left as they are nery efficient burners. Most also come with automatic feeder systems so you just fill the big hopper each day and leave it alone. Lambeth Plumbers know about biomass.Green:They are green because trees and plants absorb carbon dioxide during their lives so burning them just releases back the level that they would had they just died. So no increase in CO2 exists. Actually there is a slight net increase , because you need to process the wood and then transport it to your home, but on the whole they have a very small carbon footprint. A Lambeth Plumber is aware of carbon footprints.Another issue to consider is storage. Biomass on average is about 14 times bulkier than oil, so that to heat your home for the same amount of time you will need 14 times the area for storage. Size is also a problem for biomass burners themselves. The hopper is the bulky thing not really the boiler itself. All in all this is a very good approach for a niche market but its not a viable long term option for everyone. That being said, any landowner with access to sustainable woodland or arable by-products has to be mad if they have not already considered the use of biomass as an alternative source of producing fuel. Of course it is not the most cheap to convert, but there are grants available and a biomass boiler will, in the long term definitely pay for itself, during which time you wont be adding carbon dioxide to the atmosphere and will be able to hug a tree with a clear conscience, if it isnt already in your boiler!